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The effects of creep and fatigue on damage accumulation in ligament Schwab, Timothy David
Abstract
Ligaments are collagenous tissues that passively resist tensile forces to maintain joint stability and guide joint motion. When ligaments are damaged or are healing from an injury, they have increased laxity. Increased ligament laxity may cause increased joint laxity, which could lead to other musculoskeletal complications. As damage is thought to influence ligament laxity, it is important to understand damage mechanisms and accumulation in ligament. Ligaments can be damaged during loading and in vivo loads can be either constant (creep) or cyclic (fatigue); therefore, the effects of creep and fatigue on damage accumulation were investigated in ligament. Medial collateral ligaments were subject to in vitro, uniaxial creep or fatigue tensile loading. Testing was completed at three maximum stresses: 60%, 30% and 15% of the ultimate tensile strength. Some ligaments were loaded until rupture, and some did not rupture during loading. Behaviour of ligaments subjected to creep was compared to those subjected to fatigue at each stress level. Ligament behaviour was quantified with times-torupture, strain profiles, and stress-strain characteristics. Damage was confirmed with a stretch to failure for those ligaments that did not rupture in creep or fatigue. Fatigue loading was more damaging than creep loading. Fatigue ligaments failed sooner than creep ligaments and the strain profiles differed between the two loading profiles. On a normalized time scale, creep ligaments experienced higher strains than fatigue ligaments. When time of loading was accounted for, fatigue ligaments failed sooner, which resulted in greater strains in fatigue than creep at specific time-points. Both creep and fatigue loading resulted in changes in stress-strain characteristics. Tangent modulus was used to track damage and inputted into a continuum damage mechanics model to predict time-to-rupture of creep and fatigue. Results indicate that fatigue loading likely involves an additional damage mechanism not present in creep loading. In essence, fatigue loading involves both cycle-dependent and time-dependent damage, while creep loading only involves time-dependent damage. Therefore, loading condition (static versus cyclic) was found to affect damage accumulation in ligament. Information from this study furthers the current understanding of ligament damage accumulation.
Item Metadata
Title |
The effects of creep and fatigue on damage accumulation in ligament
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2006
|
Description |
Ligaments are collagenous tissues that passively resist tensile forces to maintain joint stability
and guide joint motion. When ligaments are damaged or are healing from an injury, they have
increased laxity. Increased ligament laxity may cause increased joint laxity, which could lead to
other musculoskeletal complications. As damage is thought to influence ligament laxity, it is
important to understand damage mechanisms and accumulation in ligament.
Ligaments can be damaged during loading and in vivo loads can be either constant (creep) or
cyclic (fatigue); therefore, the effects of creep and fatigue on damage accumulation were
investigated in ligament. Medial collateral ligaments were subject to in vitro, uniaxial creep or
fatigue tensile loading. Testing was completed at three maximum stresses: 60%, 30% and 15%
of the ultimate tensile strength. Some ligaments were loaded until rupture, and some did not
rupture during loading. Behaviour of ligaments subjected to creep was compared to those
subjected to fatigue at each stress level. Ligament behaviour was quantified with times-torupture,
strain profiles, and stress-strain characteristics. Damage was confirmed with a stretch to
failure for those ligaments that did not rupture in creep or fatigue.
Fatigue loading was more damaging than creep loading. Fatigue ligaments failed sooner than
creep ligaments and the strain profiles differed between the two loading profiles. On a
normalized time scale, creep ligaments experienced higher strains than fatigue ligaments. When
time of loading was accounted for, fatigue ligaments failed sooner, which resulted in greater
strains in fatigue than creep at specific time-points. Both creep and fatigue loading resulted in
changes in stress-strain characteristics. Tangent modulus was used to track damage and inputted
into a continuum damage mechanics model to predict time-to-rupture of creep and fatigue.
Results indicate that fatigue loading likely involves an additional damage mechanism not present
in creep loading. In essence, fatigue loading involves both cycle-dependent and time-dependent
damage, while creep loading only involves time-dependent damage. Therefore, loading
condition (static versus cyclic) was found to affect damage accumulation in ligament.
Information from this study furthers the current understanding of ligament damage accumulation.
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Genre | |
Type | |
Language |
eng
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Date Available |
2010-01-05
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0080763
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2006-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.